During the weaving of textiles, the threads are exposed to considerable mechanical strain. In order to prevent breaking, they are usually reinforced by coating ("sizing") with a gelatinous substance ("size").
The most common sizing agent is starch in native or modified form. However, other polymeric substances, for example poly-vinylalcohol (PVA), polyvinylpyrrolidone (PVP), polyacrylic acid (PAA) or derivatives of cellulose [e.g. carboxy-methylcellulose (CMC), hydroxyethylcellulose, hydroxypropyl-cellulose or methylcellulose] may also be abundant in the size. Small amounts of, e.g., fats or oils may also be added to the size as a lubricant.
As a consequence of the presence of the size, the threads of the fabric are not able to absorb water, finishing agents or other compositions (e.g. bleaching, dyeing or crease-proofing compositions) to a sufficient degree. Uniform and durable finishing of the fabric can thus be achieved only after removal of the size from the fabric; a process of removing size for this purpose is known as a "desizing" process.
In cases where the size comprises a starch, the desizing treatment may be carried out using a starch-degrading enzyme (e.g. an amylase). In cases where the size comprises fat and/or oil, the desizing treatment may comprise the use of a lipolytic enzyme (a lipase). In cases where the size comprises a significant amount of carboxymethylcellulose (CMC) or other cellulose-derivatives, the desizing treatment may be carried out with a cellulolytic enzyme, either alone or in combination with other substances, optionally in combination with other enzymes, such as amylases and/or lipases.
It is an object of the present invention to achieve improved enzyme performance under desizing conditions by modifying the enzyme so as to alter (increase) the affinity of the enzyme for cellulosic fabric, whereby the modified enzyme comes into closer contact with the sizing agent in question.